Guide bars for chain saws are usually made either laminated from three thin plates that are joined by spot welding or adhesives, or solid from one thicker plate. The latter type is preferred when the saw is subject to severe stresses. The solid plate requires machining of a circumferential groove to guide the drivelinks of the saw chain.
The machining is done either by milling or by grinding. Either method produces a groove with rough side walls, depending on feed and radial clearance. Typical average surface roughness values are Ra=5 to 10 microns.
One frequent mode of failure of guide bars is through wear of the groove to such an extent that it fails to guide the saw chain properly. Such improper guiding is manifested by vibrations and torsion stresses in the saw chain. Solid guide bars are known to wear faster and cause more wear to the saw chain than laminated bars, where the groove side walls are formed by the smooth rolled surface of the plates. To some extent hardening of the edges of the guide bar can delay the wear. However, hardening has limits since it is accompanied by brittleness and possible failure by cracking.
The present invention relates to a solid guide bar which has been further treated after machining of the groove to reduce the surface roughness of the groove.
The present invention further provides a solid guide bar which is less susceptible to failure and provides an increased useful life as well as assisting high speed operation.